Frog Deformities

Copyright 1998 American Association for the Advancement of Science
Science 1998;279:459, 461

Jocelyn Kaiser's article about the recent National Institute of Environmental Health Sciences "deformed frogs" workshop (News& Comment, 19 Dec., p. 2051) is the most accurate summary of this perplexing phenomenon I have yet read. However, a couple of points require clarification. First, a great deal of unnecessary confusion has been generated by the tendency to lump all amphibian deformities together. For example, cohorts of froglets with supernumerary limbs present a very different suite of characteristics than older metamorphosed frogs with missing limbs or limb parts, suggesting different causes, and most laboratory-induced deformities have shown little or no similarity to those seen in nature. Another point concerns whether deformities are on the rise or the scale of the problem has been overblown. An analysis of reports of deformities compiled by the North American Reporting Center for Amphibian Malformations (1) suggests the latter. Approximately half of the recent reports of deformed amphibians in the United States and Canada are from a single study (my own) of one site in California, published in 1990 (2)! More than half of the remaining deformed specimens are from intensive searches in Minnesota over the last 2 years. Furthermore, many recent reports may be questionable, for example, sightings of frogs with "retained tails."

Finally, numerous Web pages on de ormed frogs have fueled widespread controversy and alarm in the media from the very beginning, effectively performing an end-run around scientific research. I agree with David Wake (director of the Museum of Vertebrate Zoology at the University of California, Berkeley) that sorting this out could be a scientific nightmare.

Stanley K. Sessions
Department of Biology,
Hartwick College,
Oneonta, NY 13820, USA


  2. S. K. Sessions and S.B. Ruth, Exp. Zool. 254, 38 (1990).

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